1. Field of the Invention
The present invention relates to an inkjet recording device that discharges ink from an ink head and performs printing, and interrupts the path of an ink supplying system to prevent the meniscus of an ink discharging plane from being destroyed, when the device vibrates or by the device's estimation of periodic vibration thereof.
2. Description of the Related Art
In the related art, there has been an inkjet recording device that discharges ink from an ink head according to image data and prints it on a recording medium such as a printing paper. FIG. 8 is a drawing that depicts configuration of the path of a general inkjet recording device.
As shown in FIG. 8, an inkjet recording device 101 includes an exchangeable ink bottle 2 that is an ink tank, a reservoir 3 that temporarily stores the ink supplied from the ink bottle 2 and an ink head 4 that discharges the ink supplied from the reservoir 3 through the discharge entrance 5. Moreover, in this inkjet recording device 101, paths 6a and 6b are connected between the ink bottle 2 and the reservoir 3 and between the reservoir 3 and the ink head 4 respectively, to form the ink supplying system. In addition, an electromagnetic valve 7a that opens and interrupts this path 6a by controlling the opening/closing when the ink from the ink bottle 2 is supplied in the path 6a between the ink bottle 2 and the reservoir 3. Further, the ink bottle 2 includes an atmospheric opening aperture 8a to open the inside of the ink bottle 2 to atmosphere.
A waste fluid tank 12 is connected with a path to the reservoir 3 through an overflow tank 11. The overflow tank 11 has been installed to make the ink flow thereinto, for examples, when the ink supplied from the ink bottle 2 to the reservoir 3 is in excess. The ink that flows into the overflow tank 11 is accommodated by the waste fluid tank 12. Moreover, this overflow tank 11 includes an atmospheric opening aperture 8b to open the reservoir 3 to atmosphere through a path 6c. 
In addition, a pressurized pump 13 is connected with the reservoir 3. The pressurized pump 13 has been installed in order to push ink out of the ink supplying system mainly for the purge. Moreover, an electromagnetic valve 7b that controls the opening at the time of the purge and opens a path 6d between the reservoir 3 and the pressurized pump 13 is installed between the reservoir 3 and the pressurized pump 13.
An ink head 4 (inkjet head) includes an atmospheric opening aperture 8c. An electromagnetic valve 7c is installed in the atmospheric opening aperture 8c. This electromagnetic valve 7c usually opens the atmospheric opening aperture 8c, and controls the closing only when ink is filled and interrupts the atmospheric opening aperture 8c. In addition, discharge entrance 5 is disposed on the plane opposite to the printing paper of the ink head 4.
Moreover, as the ink head 4, there are, for example, a thermal method that generates air bubbles by heating and discharges the ink and a piezo method that uses a piezoelectric element to be transformed by voltage. However, any method may be adopted in this case. Moreover, a line head method in which the ink head 4 is arranged in a direction perpendicular to a transportation direction X in each color of black (K), cyan (C), magenta (M), and yellow (Y) may be adopted, and a serial head method in which the ink head 4 moves in a direction perpendicular to a transportation direction X may be adopted.
Further, each of the electromagnetic valves 7a to 7c controls the opening/closing by the valve switching control means which is not shown in the figure.
In addition, transportation means 14 to maintain a constant distance from the discharge entrance 5 and to transport printing papers in a predetermined transportation direction X is installed just below discharge entrance 5 of the ink head 4 as shown in FIG. 8. The transportation means 14 includes a pair of rollers 15 and 15 and a transportation belt 16 that is hung and turned around between rollers 15 and 15. Though not shown in the figure, one of a pair of rollers 15 and 15 is a driving roller connected with the driving means, and, the other one is a driven roller.
Moreover, the transportation belt 16 includes an endless belt. In the transportation belt 16, plural suction holes that penetrate between a surface that becomes the transportation plane of printing paper and a rear surface and not shown in the figure have been installed. In addition, the suction fan not shown in the figure is installed on the back side of the transportation belt 16. This suction fan absorbs the printing paper on the surface of the transportation belt 16 by sucking air through the suction holes while transporting the printing paper using the transportation belt 16.
However, in the inkjet recording device 101 mentioned above (FIG. 8), a meniscus is formed by generating a negative pressure on the ink discharging plane Sa by the difference of the height between an ink liquid level in the reservoir 3 and the ink discharging plane 5a at the discharge entrance 5 of the ink head 4 (water head difference H) by opening the inside of the reservoir 3 to atmosphere as shown in FIG. 9A during a printing operation by the ink head 4 or during the pause of the printing when the printing operation is not performed. However, when the inkjet recording device 101 receives impact and it vibrates for example, the ink liquid level in the reservoir 3 may change as shown in FIG. 9B, and the change of this ink liquid level may be transmitted to the meniscus of the ink discharging plane 5a, and the meniscus may break. When the meniscus breaks, air bubbles mix go into the discharge entrance 5 of the ink head 4 and it causes a defective ink discharge.
Moreover, JP-A-2005-131811 discloses the ink jet printer including the mechanism that interrupts ink supply in response to impact or vibration when the impact or the vibration is applied and prevents the ink leakage from the nozzle. As shown in FIG. 10, the ink leakage preventing mechanism 201 includes a valve body 203 that opens and closes an ink supply path 202 where ink is supplied to the ink head, a biasing member 204 that biases the valve body 203 to a close position, a weight 205, and a mounting surface 206 on which the weight 205 is movably mounted. The ink leakage preventing mechanism 201 further includes a valve control member (a first swing lever 207 and a second swing lever 208) that retains the valve body 203 to an open position by the weight of the weight 205. According to this constitution, the weight 205 separates temporarily from the mounting surface 206 when the impact or the vibration is applied to the printer and when the printer inclines. When the weight 205 separates from the mounting surface 206, the second swing lever 208 swings to disengage from a first swing lever 207 and thereby the first swing lever 207 becomes swingable. As a result, the valve body 203 moves to the close position by the bias force of the bias member 204 and interrupts the ink supply path 202, thus the ink leakage from the nozzle can be prevented.
However, because the above-mentioned ink leakage preventing mechanism (JP-A-2005-131811) controls the opening/closing of the ink supply path 202 physically, there is a slight gap of time to close the ink supply path 202 after the printer vibrated. With this configuration, it is insufficient in terms of speed to prevent transmission of the change of ink liquid level in the reservoir to the meniscus of the ink discharging plane. Furthermore, the configuration is complex and precise as shown in FIG. 10, thus work such as maintenance becomes complex.
In addition, the above-mentioned ink leakage preventing mechanism does not interrupt the ink supply path 202 if the vibration, etc. is not actually applied to the printer. Thus this mechanism is unsuitable for foreseeable vibration (for example, periodic vibration by the operation of the internal mechanism).